A transponder of the aforementioned type and a “plucking” method are known from U.S. Pat. No. 5,621,396. In order to optimise the power supply to the resonant circuit as a function, in particular, of the quality factor of the transponder, i.e. to provide sufficient power to maintain oscillation amplitude over a maximum duration, this document proposes to arrange a peak detector for the oscillating signal in the resonant circuit and to compare the peak value detected in a half-cycle of the oscillating signal with a reference voltage. As soon as the peak value is lower than this reference voltage, the resonant circuit is powered via a switch. The power is only provided periodically by identical pulses; the power frequency therefore varies according to the quality factor of the transponder.